Low voltage transformer which are sometimes referred to as a step down transformer are used to convert main line voltage to a lower voltage suitable for bulbs. Transformers can be used with incandescent, halogen, xenon and krypton type bulbs. This transformer has a "120 Volt" Input Voltage which is converted to "12" Volts. (AC) Measurements 2.63" Long x 1.38" Width x 0.88" Height. This transformer is dimmable and is fully potted. Potting helps protect the internal components from being damaged if they are exposed to the elements. Minimum wattage requirements are common for lighting transformers. This means that the transformer will not produce 12 Volts if the "20 Watt" minimum wattage amount is not applied. Always make sure power is off when working with electrical parts and fixtures. **Although it may work with some LED's it is not recommended to be used with LED bulbs.